U.S. patent number 4,496,020 [Application Number 06/452,431] was granted by the patent office on 1985-01-29 for v-type multi-cylinder engine for motorcycle.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Toshiro Mitsuishi.
United States Patent |
4,496,020 |
Mitsuishi |
January 29, 1985 |
V-Type multi-cylinder engine for motorcycle
Abstract
Disclosed is an engine for motorcycles, having first and second
engine blocks disposed in a form like V on the frame of the
motorcycle. Pistons reciprocatably and slidably received in the
engine blocks are connected to first and second crank pins of a
crankshaft through respective connecting rods. Representing the
included angle between the central axes of first and second
cylinders for the first and second piston by .alpha., the
rotational phase of the second crank pin is offset from that of the
first crank pin by an angle .pi.-2.alpha. in the opposite side of
the central axis of the first cylinder to the central axis of the
second cylinder. A balancer weight is attached to that portion of
the crank shaft positioned opposite to the first and second crank
pins and on the bisector line of the angle formed between the first
and second crank pins. With this arrangement, the primary inertia
force as applied to the crankshaft by the mass of reciprocating
parts such as pistons can be substantially eliminated to remarkably
suppress the vibration of the engine.
Inventors: |
Mitsuishi; Toshiro (Tokorozawa,
JP) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
16574113 |
Appl.
No.: |
06/452,431 |
Filed: |
December 23, 1982 |
Foreign Application Priority Data
|
|
|
|
|
Dec 26, 1981 [JP] |
|
|
56-209518 |
|
Current U.S.
Class: |
180/219;
123/192.1; 123/192.2; 123/54.4; 74/603; 74/604 |
Current CPC
Class: |
B62M
7/02 (20130101); F02B 61/02 (20130101); F02B
75/22 (20130101); F02F 7/0019 (20130101); Y10T
74/2183 (20150115); F02B 2075/1808 (20130101); Y10T
74/2184 (20150115); F02B 2075/027 (20130101) |
Current International
Class: |
B62M
7/00 (20060101); B62M 7/02 (20060101); F02B
61/02 (20060101); F02B 75/00 (20060101); F02F
7/00 (20060101); F02B 75/22 (20060101); F02B
61/00 (20060101); F02B 75/18 (20060101); F02B
75/02 (20060101); B62D 061/02 (); F16F
015/26 () |
Field of
Search: |
;180/229,225,219,218
;123/59R,53A,53R,53B,54R,55V,55VF,56B,192R,192B
;74/359,66R,603,604,49 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Peters, Jr.; Joseph F.
Assistant Examiner: Hill; Mitchell J.
Attorney, Agent or Firm: Armstrong, Nikaido, Marmelstein
& Kubovcik
Claims
What is claimed is:
1. A V-type multi-cylinder engine for motorcycles, including first
and second engine blocks arranged on a frame so as to form a V
shape, said engine blocks having first and second cylinders,
respectively, pistons reciprocatably and slidably received by said
first and second cylinders, and a crankshaft having first and
second crank pins connected through piston rods to said pistons,
wherein the improvement comprises that the rotational phase of said
second crank pin is offset from that of said first crank pin by an
angle .pi.-2.alpha. in the opposite side of the central axis of
said first cylinder to the axis of said second cylinder, .alpha.
representing an angle included between the central axes of said
first and second cylinders, and that a balancer weight is attached
to that portion of said crank shaft positioned opposite to said
first and second crank pins and on the bisector line of the angle
formed between said crank pins around said crankshaft.
2. A V-type multi-cylinder engine for motorcycles as set forth in
claim 1, wherein said first and second engine blocks are arranged
on the frame of said motorcycle in the longitudinal direction
thereof.
3. A V-type multi-cylinder engine for motorcycles as set forth in
claim 1 or 2, wherein the included angle between the central axes
of said first and second cylinders is smaller than 90.degree..
4. A V-type multi-cylinder engine for motorcycles as set forth in
claim 3, wherein the included angle between the central axes of
said first and second cylinders is 45.degree..
5. A V-type multi-cylinder engine for motorcycles as set forth in
either one of claims 2, wherein said frame includes a downtube
having first and second portions, the first portion extending
downwardly and the second portion extending rearwardly with respect
to a head pipe supporting a steering axle, and wherein said engine
blocks are disposed in a space to the rear of the first portion and
above the second portion of said downtube.
6. A V-type multi-cylinder engine for motorcycles as set forth in
claim 5, wherein said first and second engine blocks are arranged
in symmetry with each other with respect to a vertical plane
passing through the axis of rotation of said crankshaft.
7. A V-type multi-cylinder engine for motorcycles as set forth in
any one of claims 1 or 2, wherein said engine blocks are rigidly
fixed to said frame.
8. A V-type multi-cylinder engine for motorcycles as set forth in
claim 5, wherein said first and second cylinders in said first and
second engine blocks are arranged symmetrically with respect to the
longitudinal axis of said frame at equal distances offset
sidewardly from that axis.
9. A V-type multi-cylinder engine for motorcycles as set forth in
claim 8, further comprising valve actuating cam shafts rotatably
carried by said first and second engine blocks, respectively,
driven sprockets attached to said valve actuating cam shafts,
respectively, driving sprockets fixed to both ends of said
crankshaft, and endless timing chains engaging respective
combinations of said driving and driven sprockets.
10. A V-type multi-cylinder engine for motorcycles as set forth in
claim 5, wherein said first cylinder is positioned closer to said
downtube than said second cylinder and the axis of said first
cylinder is parallel to the first portion of said downtube.
Description
BACKGROUND OF THE INVENTION
Brief Description of the Invention
The present invention relates to a V-type multicylinder engine for
motorcycles, and more particularly to an engine having a plurality
of cylinders disposed in a V shape and a crankshaft common to those
cylinders.
Description of the Prior Art
When mounting the aforementioned V-type multi-cylinder engine to a
motorcycle, an attempt has hitherto been made to alleviate the
vibration of a crankshaft as well as a chassis by eliminating the
first term of ill-balanced intertia force applied to the common
crankshaft by the mass of reciprocating parts such as pistons and
the like, which parts reciprocate in cylinders, by disposing the
cylinders in a form like V with an included angle 90.degree.
therebetween and by attaching an appropriate balancer weight to the
crankshaft.
However, in the case where the included angle between cylinders is
made smaller than 90.degree. for reduction of the engine disposing
space, when pistons reciprocating in a plurality of cylinders are
connected to a common crank pin of the crankshaft via connecting
rods, it was impossible to eliminate the primary term of the
ill-balanced inertia force resulting from the aforementioned mass
of the reciprocating parts even by attaching a balancer weight to
the crankshaft. Consequently, the vibration of the crankshaft,
which is transmitted to the chassis, constituted a problem of
unfavorably deteriorating the riding comfort of the rider.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a
compact V-type multi-cylinder engine for motorcycles of the type
mentioned above designed to substantially reduce the vibration,
thereby to eliminate the above-described problem of the prior
art.
To this end, according to the invention, there is provided a V-type
multi-cylinder engine including first and second engine blocks so
arranged on a frame as to form a V shape and having first and
second cylinders, respectively, pistons slidably fitted in the
first and second cylinders, and a crankshaft having first and
second crank pins connected to the first and second pistons via
piston rods, wherein the improvement comprises that the rotational
phase of the second crank pin is offset from that of the first
crank pin by an angle .pi.-2.alpha. in the opposite side of the
central axis of the first cylinder to the central axis of the
second cylinder, .alpha. representing the included angle between
the central axes of the first and second cylinders, and that a
balancer weight is attached to that portion of the crankshaft
positioned opposite to the first and second crank pins and on a
bisector line of the angle formed between the first and second
crank pins around the crankshaft.
The above and other objects, features and advantages of the present
invention will be apparent from the following detailed description
of a preferred embodiment when taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a motorcycle equipped with an engine in
accordance with the present invention;
FIG. 2 is a partly-sectioned plan view of the motorcycle as shown
in FIG. 1;
FIG. 3 is a partially enlarged view illustrating how the engine is
mounted on the frame;
FIG. 4 is a cross sectional view taken along the lines IV--IV in
FIG. 1;
FIG. 5 is an enlarged side elevational view showing the general
arrangement of pistons, connecting rods and crankshaft; and
FIG. 6 is an explanatory drawing illustrating the principle of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will be described
hereinunder with reference to the attached drawings.
Drawings show a motorcycle mounting a V-type multi-cylinder engine
constructed in accordance with the present invention (a
two-cylinder engine in the illustrated example).
Referring first to FIG. 1, a two-cylinder engine 2 having a pair of
engine blocks 3 and 4 mounted on a frame 1 of the motorcycle in
such a manner as to form a V shape in the longitudinal direction of
the chassis, and a common crankshaft 5 is disposed at right angles
to the longitudinal direction of the chassis.
The engine 2 is disposed on the cradle-type frame, and the front
cylinder block 3 of the engine 2 is arranged in such a way that its
central axis 3a is substantially parallel with a downtube 7
extending from a head pipe 6 of the frame 1 downwardly towards the
rear end of the chassis.
To reduce the length of the engine 2 in the longitudinal direction
of the chassis, the front and rear engine blocks 3 and 4 are
arranged such that the included angle between their central axes 3a
and 4a becomes smaller than 90.degree. (in the illustrated
drawings, approximately 45.degree. ). Also, the front and rear
engine blocks 3 and 4 are arranged so that the central axes 3a and
4a become symmetric, i.e., at equal angles, with respect to a
vertical plane P passing the central axis of rotation of the
crankshaft 5.
As shown in FIG. 4, each of the front and rear engine blocks 3 and
4 is composed of front and rear cylinders 15 and 16, respectively,
as well as front and rear cylinder heads 23 and 24 secured to the
top side of the respective cylinders 15 and 16, the cylinders 15
and 16 being arranged symmetrically by offsetting their central
axes 3a and 4a at a fixed distance .epsilon. toward both sides of
the vertical central line l of the chassis, as shown in FIG. 2.
The crankshaft 5 is rotatably supported by a crank and transmission
case 8 at a point of intersection between the central axes of the
front and rear engine blocks, i.e., the central axes 3a and 4a of
the front and rear cylinders 15 and 16. Pistons 17 and 18 slidably
received by front and rear cylinders 15 and 16 are connected to
first and second crank pins 11 and 12 of this crankshaft 5 via
first and second connecting rods 13 and 14.
Driving sprockets 21 and 22 are fixed to both ends of the
crankshaft 5. Driven sprockets 27 and 28 are fixed on the
oppositely positioned sides of valve actuator camshafts 25 and 26,
respectively, which camshafts 25 and 26 are rotatably supported on
respective top portions of front and rear cylinder heads 23 and 24.
Endless timing chain 29 goes round between the driving and driven
sprockets 21 and 27 and another endless timing chain 30 between
sprockets 22 and 28, so that the rotation of the crankshaft 5 is
transmitted to the valve actuator camshafts 25 and 26 via the
timing chains 29 and 30, respectively.
If the engine blocks 3 and 4 are disposed in such a way that the
included angle .alpha. between the respective central axes 3a and
4a become smaller than 90.degree., as mentioned earlier, it is
impossible to eliminate the primary term of inertia force resulting
from the mass of reciprocating parts such as pistons 17 and 18 even
by attaching a balancer weight to the crankshaft 5 in conventional
cases where the pistons 17 and 18 inside the front and rear
cylinders 15 and 16 are connected to the common crank pin of the
crankshaft 5.
Therefore, in accordance with this invention, the primary term of
this inertia force can be eliminated by connecting the first and
second connecting rods 13 and 14 to separate crank pins 11 and 12
of the crankshaft 5 and by providing a phase differential between
these crank pins 11 and 12 by a predetermined angle
(.pi.-2.alpha.). The reason for this shall be explained
hereinunder.
First, if the central axis 3a of the front cylinder 15 is taken as
the X axis and a straight line perpendicular to the central axis 3a
and passing a point of intersection 0 between the central axes 3a
and 4a of the front and rear cylinders 15, 16 as the Y axis, the
component in the direction of the X axis of the primary inertia
force, Fx, of the mass of the reciprocating parts such as pistons
17 and 18 can be obtained as the composite force of the X axis
component Fxa of the primary inertia force chiefly produced by the
piston 17 and the X axis component Fxb of the primary inertia force
chiefly produced by the piston 18. In other words,
Where
Ma: the mass of reciprocating parts, including the piston 17,
imposed upon the first crank pin 11
Mb: the mass of reciprocating parts, including the piston 18,
imposed upon the second crank pin 12
ra: the radius of rotation of the first crank pin 11
rb: the radius of rotation of the second crank pin 12
.omega.: the angular velocity of the crankshaft 5
.theta.: the rotational angle of the first crank pin 11
.alpha.: the included angle between the central axes 3a and 4a of
cylinders 15 and 16
.beta.: the angle formed between the second crank pin 12 and an
extension of the central axis 4a of the cylinder 16 in the initial
period of rotation (.theta.=0)
Also, the component in the Y axis direction, Fy, of the primary
inertia force of the mass Ma, Mb of reciprocating parts is obtained
in terms of the composite force between the Y axis component Fya of
the primary inertia force chiefly produced by the piston 17 and the
Y axis component Fyb of the primary inertia force chiefly produced
by the piston 18. In other words, ##EQU1##
Furthermore, if the mass Ma, Mb of reciprocating parts is equalized
and the radii ra, rb of rotation of the first and second crank pins
11 and 12 are also equalized, then the composite force Fx of the
primary inertia force in the direction of X axis can be expressed
as follows: ##EQU2##
Also, the composite force Fy of the primary inertia force in the
direction of Y axis can be expressed as follows: ##EQU3##
Accordingly, the absolute value of the vector F combining the X
axis component Fx and the Y axis component Fy of the aforementioned
primary inertia force is as follows: ##EQU4##
If it is assumed that sin .alpha.=r, cos .alpha.=S, sin .beta.=P
and cos .beta.=Q,
then, ##EQU5##
In order to balance the aforementioned primary inertia force, i.e.,
the composite vector F, the following conditions must be met
simultaneously.
(1) The magnitude of F (.vertline.F.vertline.), i.e., Z, must be
fixed.
(2) The direction and velocity of rotation of .vertline.F.vertline.
must be those of the crankshaft 5.
Therefore, an examination shall be made first with respect to the
first condition, Z.ident.k (k: constant).
First, the formula: ##EQU6## shall be transformed as follows:
If in this stage are provided the following three conditions:
##EQU7## there is achieved the following transformation:
##EQU8##
If the above equation is to be held irrespective of the value of
.theta., then the condition of t=0 must be satisfied.
Therefore,
Since
If it is assumed that .beta.=.alpha.+2.pi.n, ##EQU9##
Therefore, the rotational direction and the angular velocity of the
composite vector F becomes the same as those of the crankshaft 5
when .beta.=.alpha.+2.pi.n.
Also, if it is assumed that .beta.=-.alpha.+2.pi.n, ##EQU10##
Therefore, the rotational direction and the angular velocity of the
composite vector F is opposite in direction to those of the
crankshaft 5 when .beta.=-.alpha.+2.pi.n.
Also, when .beta.=.alpha.+2.pi.n, the absolute value of the
composite vector F is as follows: ##EQU11##
It can be seen from the above that the elimination of the primary
vibration resulting from the mass of the reciprocating parts by
attaching a balancer weight to the crankshaft 5 can be achieved
only when .beta.=.alpha.+2.pi.n. Hence, this can be achieved by
offsetting the phase of the second crank pin 12 against the first
crank pin 11 by .pi.-(.alpha.+.beta.), that is, .pi.-2.alpha. in
the direction opposite to the direction of the central axis 4a of
the cylinder 16 from the central axis 3a of the cylinder 15, and by
adding the balancer weight 31 having the same magnitude as the
composite vector F to the crankshaft 5 in such a way as to offset
the phase of its center of gravity by .pi. from the composite
vector F, namely, on the opposite side of the composite vector
F.
According to the construction described hereinbefore, the vibration
of the engine 2 can be attenuated substantially so that the engine
2 can be mounted simply rigidly on the frame by means of a fixing
means 32 such as a bolt, as shown in FIGS. 1 and 3, without
resorting to conventional rubber mounting method.
In the foregoing embodiment, two engine blocks 3, 4 are disposed in
a V shape along the longitudinal direction of the chassis, but they
may be disposed in a V shape in the direction transverse to the
chassis.
It is to be noted also that the invention can be applied not only
to V-type twin cylinder engines but also to V-type multi-cylinder
engines having more than two cylinders arranged in a form like
V.
* * * * *